I think ageing is definitely related to the opé opé no mi, however it doesn't mean they are invincible.
For me their invincibility looks related to the Lunaria and the black flame, similarly to King's and the new Pacifista's power. It also means they have a weakness that currently only Zorro...
It's neither Arabasta or Alabasta, but the Japanese which is ambivalent. It makes sense since oda like puns. It has been translated both ways.
I see a huge amount of ancient Egyptian and some Indian themes, as well as Arab/Persian architecture, so it all makes sense. I would prefer Alabasta...
Alabasta is not odd but actually referring to the greek name Alabaster, a white stone used in ancient Egyptian sculpture. Alabastron is also the greek name of Akhetaton, near Thebes where this stone was extracted.
The 8 scabbards crying over Kanjuro and its death being off panel can mean a later revelation: imo Kanjuro was not a voluntary traitor, but being blackmailed from the start, with something so bad that he could only lie or die for it.
Maybe Orochi is not dead but he's such a loser anyway...
I think Komurasaki is Hiyori, Oden's daughter, planning her revenge. Unless Kiku is Hiyori, which might also fit.
Then Komurasaki must be Alvida or Boa Hancock.
In any case it must be someone we know, otherwise I wouldn't see the point of hiding her face.
Unless it is a big joke: an o-kama...
Well we have been given a hint on the technique to steal a devil fruit from how Big Mom got hers : by eating her mentor.
Since Whitebeards body was mostly intact after Blackbeard stole his power, my guess is that you've got to eat the person's heart or brain.
We can speculate as to what are the...
Prediction : Jewelry Bonney is the 7th Shichibukai (as there is no reason that Akainu would have freed her otherwise)
Crazy Theory :
The hearts that Law delivered to become Shichibukai were his nakamas'.
Their bodies are frozen on Punk Hazard for conservation until he retrieves them.